Shiretoko has a lot to offer, at a price. You can technically get here with public transportation but getting around seems a little difficult. I drove in Hokkaido for the entire duration and it was well worth it to explore not only the north of Japan but also the Shiretoko area itself. I stayed at a luxurious hotel (Daiichi, which has a five star buffet if you ask me) which is unusual for me but seemed to match the trip. The hotel (as third party) offers a boat cruise but the weather in October wasn't good enough for the boat to ever depart so I never got to see the northern tip of Shiretoko NP (Mountain) from the boat and there is no other way to get there. The road at the western side enables you to see some wildlife, especially deer, which was great in itself but doesn't really "go" anywhere. There is a famous pass (see pic) as you get over to the east side and there is another road going north which is very similar for both content and views. There are many onsen (hotsprings) around the area but the hotel already offered that so I didn't need to waste exploring time on that.
The easiest and one of the better ones to enjoy is the boardwalk along the Shiretoko Five Lakes. It's easy, very green, very fresh and lots of info to read about. You would usually see migratory birds here but I was already too late for that. The park has a lot to offer throughout the seasons but as a tourist you'll only enjoy the summer.